How do solar panels work in the sunshine?

How-rooftop-solar-works

Let me just say that how solar panels work with solar energy is like how we work with coffee. Solar energy is like a dose of caffeine to the solar panels. As silly as this analogy may sound, this is how I understood the technology behind the solar panels before. And let me explain why it makes sense. 

Of course, solar panel is not the only part of the system that powers your home. We will also look at what other equipments are used in a common solar electric system. Then, finally, we will go over how everything works together to convert solar energy into electrical energy.

Let’s jump right in.

How solar panel system works – the technology behind solar cell

A solar cell is the smallest unit of a solar panel.

solarcell-solarpanel

At the heart of each solar cell is a technology called Photovoltaic. Pronounced as Photo-vol-tey-ik

Photovoltaic – The technology

Because it is always fun, let’s decode the name first: Photovoltaic, or PV in short.

Photo = Light

Voltaic = Volt

And you guessed it right. It is a Greek word. The wording is pretty straightforward for what it represents.

Photovoltaic is essentially an effect or a phenomenon that converts solar energy into electricity. When the sun comes out, solar cells go to work. The PV effect in each solar cell produces electricity – in small amount. When combined, the cumulative amount of electricity generated from a solar panel is quite significant.

How solar cells, a.k.a PV cells, work ?

As I mentioned before, photovoltaic is at the heart of every solar cell. But before I go too deep on that, a little background…

Traditionally, solar cell is made of silicon. Silicon is extracted from sand. And you can find sand everywhere – which is one of the reasons why silicon was chosen for solar cell. Silicon is cheap and the scientists really love its chemical properties as well.

That said, besides silicon, second and third generation of solar cells are being made out of different elements such as Cadmium Telluride. But silicon, normally in its crystal form, still dominates the solar industry – like google for search engine.

Now, the main part..

What I am about to explain next is crucial in your understanding of how solar cells work. Pay close attention to fully grasp the concept. 

Electricity is nothing but flow of charge, positive and negative. The power cable that is hooked up to your computer now is carrying billions of electrons at a time. We call that electricity charge.

The problem is that the silicon itself can’t push out the electrons from the solar cells. This is because the electrons are naturally bonded together in a crystal silicon. And that’s a big problem until..

silicon-crystal-lattice-bonding

…until we knock the electrons loose. This is very important because electrons are charge carriers. If they are not loose they can’t carry the charge from point A to point B.

By adding chemical impurities – the process is called doping – electrons can be knocked loose. Boron and Phosphorous are the two common impurities doped in the silicon. 

See below for simple visualization.

doping-silicon-solar

What happens when the sun shines?

How these doped silicon solar cells work in the sunshine is quite interesting.

If you recall, after doping we were left with positively and negatively charged loose electrons in the silicon. Unfortunately, these free charges don’t have enough energy to make any impact.

Of course, that changes when the big bright sun comes out.

Sunlight excites the free electrons which then start to vibrate and drift. And finally, the energized electrons start to flow. If you recall, the flow of electrons is electricity. 

This whole phenomenon of solar cell working is known an Photovoltaic.

See the diagram below.

 

how-solar-cells-work

As you can see, the physics behind how the solar cells work can get complex depending on what background you come from. Nonetheless, it is always easier to remember with an analogy. So, if you are like me, you may find the caffeine analogy I mentioned at the very beginning helpful. The only time I am “producing” is when I am in the “energized” state. And just like sunlight for solar cells, caffeine is quite energizing for my body.

Before, we move on to the second part of this post, I would like to share an animated video on how solar panels work. This is a really good comprehensive video that was made for TED Education. I really liked it. I hope you do too.

Next, we will talk about the equipments that are used in a common solar electric system. And after that, we will put it all together for the entire process of how solar panel system works for your home. Both these are going to be a much shorter topic than the one we just wrapped up.

How solar panel system works – The equipments

The most common type of solar electric system that is installed today has just one more component besides the solar panels – inverter.

Inverter

The kind of current that flows out of solar panels is called DC – Direct Current.

However, our household appliances use different type of current called AC – Alternating current.

To make the solar electricity work, the high voltage (400-600V) DC current is passed through a device called inverter. The output of an inverter is a lower voltage (240V) AC current.

Modern inverters can do a lot more than just flip the current from DC to AC. But that can be a separate topic of discussion for some other times.

Here is what a modern inverter looks like from one of the best inverter manufacturers in the world.

SMA-inverter

Note: Batteries can be part of a solar electric system. Because they are so pricey today, it is not all that common yet.

And now, the last topic of this post…

HOW SOLAR PANEL SYSTEM WORKS – the process

We discussed the technology behind how solar cells work. Then we talked about the inverter. Now it is just a matter of connecting the dots to understand the process.

Here is a nice diagram that demonstrate the entire process.

 

Wrapping up..

The only moving parts in a solar panel system are…. the electrons. Which is why the panels work so well and last for very long time, up to 30 years. The fuel source – solar energy – is clean, renewable and always free. At nighttime, solar panels do not produce any electricity because the photovoltaic effect can’t take place.

I hope you enjoyed reading as much as I enjoyed putting it together. If you have any questions or comments, please don’t hesitate to leave a note.

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